The Washington Post today has printed today a very bad letter from Secretary of Education Arne Duncan.

The letter is in response to an article — no great shakes either, by the way — that the Post ran earlier this week about the Wake County, N.C., school board, which recently ended a policy of reassigning children away from the schools closest to them in order to achieve greater socioeconomic diversity in the county’s schools.

Duncan’s letter calls the move “troubling,” indicating that he has already prejudged the matter, which is the subject of a complaint that has been filed with his department by the NAACP and an ongoing investigation by his Office for Civil Rights. Strike one.

The reason he finds the move troubling is that it will assertedly lead to less racial diversity in the county’s schools, and Duncan further asserts that this will have bad educational and social outcomes. But social scientists disagree on whether greater racial diversity in public schools has any positive effects at all, and even if there are some marginal positive effects, school boards can legitimately conclude that the social and monetary costs of race-based student assignments outweigh them. Strike two.

More fundamentally, if the now-rescinded policy was used with an eye toward achieving particular racial results, that would raise serious problems under the federal civil-rights laws that Secretary Duncan is supposed to be enforcing. Such race-based student assignments would also be inconsistent with the American “core values” and “racial equality” that he cites. Strike three.

In sum, Secretary Duncan’s letter indicates that he believes that children should be assigned to schools on the basis of their skin color, in order to achieve a particular politically correct racial balance. This is racial discrimination, and it is quite at odds with the dream of Dr. King — the memory of whom Duncan ironically invokes — that children not be judged by the color of their skin.